1. Field of the Invention
This invention relates to an electronic device using a carbon element linear structure typified by a carbon nano-tube and a production method thereof. More particularly, the invention relates to an electronic device having a fine structure using as its constituent element a carbon element linear structure that is expected to be a break-through in the miniaturization of Si technology, and a production method thereof.
2. Description of the Related Art
One of the important technologies in production of electronic devices is a Si technology. However, miniaturization by a top-down system in photolithography in the Si technology involves a limit, and expectations have been increasing for carbon nano-tubes and carbon fibers (carbon nano-fibers) the application of which has been proposed to constitute a fine structure by a bottom-up system in future.
To form carbon nano-tubes in a desired region on a substrate for producing an electronic device, a method has been employed that arranges a catalyst metal film, necessary for growing the carbon nano-tubes, at a desired position and then grows the carbon nano-tubes on the catalyst metal by use of a thermal CVD method or a plasma CVD method.
An element such as Ni, Fe or Co, or alloys containing these elements, are used as the catalyst metals for growing the carbon nano-tubes. For example, as shown in FIG. 1, a Ni film 12 (having a thickness of about 100 nm) deposited onto a Si substrate 10 is used as the catalyst, and the carbon nano-tubes 14 grow with an aggregation of the Ni atoms of the film 12 as the nucleus of the growth.
When the carbon nano-tubes 14 are allowed to grow with the Ni film 12 as the catalyst, the Ni amounts at the growth nuclei of the carbon nano-tubes are not constant (variation occurs at each growth nucleus) because a greater amount of Ni of the film 12 exists than the amount required for the growth of the carbon nano-tubes. In consequence, non-uniformity of the diameters of the carbon nano-tubes occurs as shown in FIG. 1.
Non-uniformity of the diameters of the carbon nano-tubes might govern performance of the electronic device fabricated by utilizing the carbon nano-tubes. For example, carbon nano-tubes having properties analogous to those of semiconductors have a band gap dependent on the diameter. When the carbon nano-tubes have semiconductor-like properties and non-uniform diameters, the characteristics of the electronic device are unstable.